U.S. patent number 10,933,697 [Application Number 15/747,741] was granted by the patent office on 2021-03-02 for pneumatic tire.
This patent grant is currently assigned to The Yokohama Rubber Co., LTD.. The grantee listed for this patent is The Yokohama Rubber Co., LTD.. Invention is credited to Masatoshi Kuriyama, Noboru Kuwahara.
![](/patent/grant/10933697/US10933697-20210302-D00000.png)
![](/patent/grant/10933697/US10933697-20210302-D00001.png)
![](/patent/grant/10933697/US10933697-20210302-D00002.png)
![](/patent/grant/10933697/US10933697-20210302-D00003.png)
![](/patent/grant/10933697/US10933697-20210302-D00004.png)
![](/patent/grant/10933697/US10933697-20210302-D00005.png)
![](/patent/grant/10933697/US10933697-20210302-D00006.png)
![](/patent/grant/10933697/US10933697-20210302-D00007.png)
![](/patent/grant/10933697/US10933697-20210302-D00008.png)
United States Patent |
10,933,697 |
Kuriyama , et al. |
March 2, 2021 |
Pneumatic tire
Abstract
A pneumatic tire comprises a tread surface comprising main
grooves extending in a tire circumferential direction, at least two
of the main grooves adjacent in the tire circumferential direction
having a wave shape with periodic oscillation; adjacent land
portions in a tire lateral direction formed by the main grooves;
lug grooves disposed in a row in the tire circumferential direction
in the land portion formed between the wave-shaped main grooves,
the lug grooves intersecting the tire circumferential direction and
communicating with the wave-shaped main grooves at both ends; and
narrow grooves disposed between pairs of the lug grooves adjacent
in the tire circumferential direction in a row in the tire
circumferential direction, the narrow grooves intersecting the tire
circumferential direction, communicating with one of the main
grooves at a first end, terminating within the land portion at a
second end, and having a narrower groove width than the lug
grooves.
Inventors: |
Kuriyama; Masatoshi (Hiratsuka,
JP), Kuwahara; Noboru (Hiratsuka, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
The Yokohama Rubber Co., LTD. |
Tokyo |
N/A |
JP |
|
|
Assignee: |
The Yokohama Rubber Co., LTD.
(N/A)
|
Family
ID: |
1000005392514 |
Appl.
No.: |
15/747,741 |
Filed: |
July 8, 2016 |
PCT
Filed: |
July 08, 2016 |
PCT No.: |
PCT/JP2016/070318 |
371(c)(1),(2),(4) Date: |
January 25, 2018 |
PCT
Pub. No.: |
WO2017/018174 |
PCT
Pub. Date: |
February 02, 2017 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20180215206 A1 |
Aug 2, 2018 |
|
Foreign Application Priority Data
|
|
|
|
|
Jul 27, 2015 [JP] |
|
|
JP2015-147931 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60C
11/04 (20130101); B60C 11/125 (20130101); B60C
11/12 (20130101); B60C 11/0306 (20130101); B60C
11/032 (20130101); B60C 11/1392 (20130101); B60C
11/0304 (20130101); B60C 11/01 (20130101); B60C
11/1236 (20130101); B60C 11/13 (20130101); B60C
11/1204 (20130101); B60C 2011/013 (20130101); B60C
2011/0355 (20130101); B60C 2011/1209 (20130101); B60C
2011/0381 (20130101); B60C 2011/1295 (20130101); B60C
2011/0348 (20130101); B60C 2011/0367 (20130101); B60C
2011/0353 (20130101); B60C 2011/0358 (20130101); B60C
2011/1213 (20130101); B60C 2011/1361 (20130101); B60C
2011/0346 (20130101); B60C 2011/0365 (20130101) |
Current International
Class: |
B60C
11/12 (20060101); B60C 11/04 (20060101); B60C
11/01 (20060101); B60C 11/13 (20060101); B60C
11/03 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
102011050705 |
|
Dec 2012 |
|
DE |
|
0855292 |
|
Nov 2002 |
|
EP |
|
S61-175104 |
|
Aug 1986 |
|
JP |
|
H10-211805 |
|
Aug 1998 |
|
JP |
|
2004-090769 |
|
Mar 2004 |
|
JP |
|
2010-089720 |
|
Apr 2010 |
|
JP |
|
2012066797 |
|
Apr 2012 |
|
JP |
|
2012-201335 |
|
Oct 2012 |
|
JP |
|
2013-193464 |
|
Sep 2013 |
|
JP |
|
2014-076764 |
|
May 2014 |
|
JP |
|
WO 2004/024471 |
|
Mar 2004 |
|
WO |
|
WO 2013/137193 |
|
Sep 2013 |
|
WO |
|
Other References
International Search Report for International Application No.
PCT/JP2016/070318 dated Oct. 18, 2016, 4 pages, Japan. cited by
applicant.
|
Primary Examiner: Maki; Steven D
Assistant Examiner: Williams; Cedrick S
Attorney, Agent or Firm: Thorpe North & Western
Claims
The invention claimed is:
1. A pneumatic tire, comprising: a tread surface of a tread portion
comprising a plurality of main grooves extending in a tire
circumferential direction, at least two of the plurality of main
grooves adjacent in the tire circumferential direction having a
wave-like shape with periodic oscillation, the plurality of main
grooves comprising four main grooves each having periodic
oscillation; a plurality of land portions adjacent to one another
in a tire lateral direction formed by the plurality of main
grooves, the plurality of land portions comprising a center land
portion, middle land portions adjacent to the center land portion
on either side in the tire lateral direction and shoulder land
portions outwardly adjacent to the middle land portions in the tire
lateral direction; the center land portion and a first middle land
portion of the middle land portions comprising a plurality of lug
grooves and a plurality of narrow grooves; the plurality of lug
grooves disposed in a row in the tire circumferential direction in
each of the center land portion and the first middle land portion
formed between the main grooves having the wave-like shape, the
plurality of lug grooves each intersecting the tire circumferential
direction and communicating at both ends with the main grooves
having the wave-like shape; and the plurality of narrow grooves
disposed between pairs of the plurality of lug grooves adjacent in
the tire circumferential direction in a row in the tire
circumferential direction, the plurality of narrow grooves each
intersecting the tire circumferential direction, communicating with
one of the main grooves at a first end, terminating within the
center land portion and the first middle land portion at a second
end, and having a narrower groove width than the plurality of lug
grooves; a second middle land portion of the middle land portions
comprising an auxiliary groove that extends in a linear manner in
the tire circumferential direction and has a narrower groove width
than the plurality of main grooves; and a plurality of through lug
grooves continuously passing through the first middle land portion
and the center land portion and terminating within the second
middle land portion without reaching the auxiliary groove.
2. The pneumatic tire according to claim 1, wherein: the auxiliary
groove divides the second middle land portion into rib land
portions adjacent in the tire lateral direction; and the rib land
portions are not divided in the tire circumferential direction by
the lug grooves.
3. The pneumatic tire according to claim 1, wherein the auxiliary
groove has a groove width ranging from 1 mm to 3 mm.
4. A pneumatic tire, comprising: a tread surface of a tread portion
comprising a plurality of main grooves extending in a tire
circumferential direction, at least two of the plurality of main
grooves adjacent in the tire circumferential direction having a
wave-like shape with periodic oscillation, the plurality of main
grooves comprising four main grooves each having periodic
oscillation; a plurality of land portions adjacent to one another
in a tire lateral direction formed by the plurality of main
grooves, the plurality of land portions comprising a center land
portion, middle land portions adjacent to the center land portion
on either side in the tire lateral direction and shoulder land
portions outwardly adjacent to the middle land portions in the tire
lateral direction; the center land portion and a first middle land
portion of the middle land portions comprising a plurality of lug
grooves and a plurality of narrow grooves; the plurality of lug
grooves disposed in a row in the tire circumferential direction in
each of the center land portion and the first middle land portion
formed between the main grooves having the wave-like shape, the
plurality of lug grooves each intersecting the tire circumferential
direction and communicating at both ends with the main grooves
having the wave-like shape; and the plurality of narrow grooves
disposed between pairs of the plurality of lug grooves adjacent in
the tire circumferential direction in a row in the tire
circumferential direction, the plurality of narrow grooves each
intersecting the tire circumferential direction, communicating with
one of the main grooves at a first end, terminating within the
center land portion and the first middle land portion at a second
end, and having a narrower groove width than the plurality of lug
grooves; a second middle land portion of the middle land portions
comprising an auxiliary groove that extends in a linear manner in
the tire circumferential direction and has a narrower groove width
than the plurality of main grooves, and a plurality of middle land
portion narrow grooves being disposed in a row in the tire
circumferential direction, the plurality of middle land portion
narrow grooves each intersecting the tire circumferential
direction, communicating with the main groove located outward in
the tire lateral direction and the auxiliary groove at both end
portions, and having a narrower groove width than the plurality of
lug grooves.
5. The pneumatic tire according to claim 4, wherein the second
middle land portion comprises a plurality of middle land portion
lug grooves disposed in a row in the tire circumferential
direction, the plurality of middle land portion lug grooves each
intersecting the tire circumferential direction, communicating with
the main groove located inward in the tire lateral direction at a
first end, and terminating within the second middle land portion at
a second end without reaching the auxiliary groove; and a plurality
of communication narrow grooves connecting terminating ends of the
plurality of middle land portion lug grooves to the auxiliary
groove and having a narrower groove width than the plurality of
middle land portion lug grooves.
6. The pneumatic tire according to claim 5, further comprising a
plurality of lug narrow grooves in which a lug groove and a narrow
groove are present disposed between the plurality of middle land
portion lug grooves and the plurality of communication narrow
grooves.
7. The pneumatic tire according to claim 4, wherein the shoulder
land portions comprise a plurality of shoulder land portion lug
grooves disposed in a row in the tire circumferential direction,
the plurality of shoulder land portion lug grooves each
intersecting the tire circumferential direction and terminating
without reaching the main groove located inward of the shoulder
land portion in the tire lateral direction; and a shoulder land
portion narrow groove disposed between pairs of the plurality of
shoulder land portion lug grooves adjacent in the tire
circumferential direction, the shoulder land portion narrow groove
intersecting the tire circumferential direction, communicating with
the main groove located inward of the shoulder land portion in the
tire lateral direction at an end portion, and having a narrower
groove width than the plurality of shoulder land portion lug
grooves.
8. The pneumatic tire according to claim 7, wherein in a first
shoulder land portion of the shoulder land portions, a plurality of
the shoulder land portion narrow grooves are disposed in a row in
the tire circumferential direction between pairs of the shoulder
land portion lug grooves adjacent in the tire circumferential
direction.
9. The pneumatic tire according to claim 8, wherein the shoulder
land portions comprise a plurality of recessed portions formed at
an outer end in the tire lateral direction; and the plurality of
shoulder land portion narrow grooves terminate at the plurality of
recessed portions at an outer end portion in the tire lateral
direction.
10. The pneumatic tire according to claim 8, further comprising a
plurality of communication narrow grooves connecting terminating
ends of the plurality of shoulder land portion lug grooves and the
main groove located inward of the shoulder land portion in the tire
lateral direction and having a narrower groove width than the
plurality of shoulder land portion lug grooves.
11. The pneumatic tire according to claim 10, further comprising a
plurality of lug narrow grooves in which a lug groove and a narrow
groove are present disposed between the plurality of shoulder land
portion lug grooves and the plurality of communication narrow
grooves.
12. The pneumatic tire according to claim 10, wherein the main
groove located inward of a second shoulder land portion of the
shoulder land portions in the tire lateral direction comprises a
plurality of bulge grooves at positions corresponding to the
plurality of communication narrow grooves that bulge toward an
adjacent second middle land portion.
Description
TECHNICAL FIELD
The present technology relates to a pneumatic tire that can provide
enhanced wear resistance performance while maintaining braking
performance on wet road surfaces.
BACKGROUND ART
The conventional pneumatic tire described in Japanese Unexamined
Patent Application Publication No. 2014-076764, for example, is
designed to improve both wet performance (braking performance on
wet road surfaces) and noise performance (anti-external noise
performance). This pneumatic tire includes a plurality of
wave-shaped circumferential grooves extending in the tire
circumferential direction with left and right groove walls having a
wave-like shape with a wavelength and an amplitude, and at least
one row of wave-shaped land portions defined by adjacent
wave-shaped circumferential grooves. The shape of the left and
right groove walls of the wave-shaped circumferential grooves have
identical wavelengths but with a phase difference. The groove wall
on the wave-shaped land portion side of one of the left and right
wave-shaped circumferential grooves that define the row of
wave-shaped land portions has an amplitude that is greater than
that of the groove wall on the wave-shaped land portion side of the
other wave-shaped circumferential groove.
The conventional heavy duty pneumatic tire described in Japanese
Unexamined Patent Application Publication No. 61-175104, for
example, is designed to improve both wet performance (braking
performance on wet road surfaces) and uneven wear resistance
performance. This heavy duty pneumatic tire includes a tread that
includes at least three main grooves extending in the tire
circumferential direction in a zigzag manner that define the tread
in the tire lateral direction, shoulder ribs located at least on
the outermost sides in the tire lateral direction on the tread, and
second ribs inwardly adjacent to the shoulder ribs that divide the
main grooves. The ridge lines of the shoulder ribs and the second
ribs that face the main grooves located outward in the tire lateral
direction have a smaller zigzag pitch and amplitude.
In the pneumatic tire of Japanese Unexamined Patent Application
Publication No. 2014-076764 described above, the wave-like shape of
the left and right groove walls of the wave-shaped circumferential
grooves provide improved braking performance on wet road surfaces.
However, improving the rigidity of the land portions to enhance
wear resistance performance may decrease the braking performance on
wet road surfaces. In the heavy duty pneumatic tire of Japanese
Unexamined Patent Application Publication No. 61-175104 described
above, the ridge lines of the shoulder ribs and the second ribs
that face the main grooves located outward in the tire lateral
direction have a smaller zigzag pitch and amplitude. The resulting
difference in rigidity may adversely affect wear resistance
performance. Additionally, the corner portions formed by the zigzag
shape of the main grooves may experience uneven wear.
SUMMARY
The present technology provides a pneumatic tire that can provide
enhanced wear resistance performance while maintaining braking
performance on wet road surfaces.
A pneumatic tire according to an embodiment of the present
technology comprises:
a plurality of main grooves extending in a tire circumferential
direction, at least two of the plurality of main grooves adjacent
in the tire circumferential direction having a wave-like shape with
periodic oscillation;
a plurality of land portions adjacent to one another in a tire
lateral direction formed by the plurality of main grooves;
a plurality of lug grooves disposed in a row in the tire
circumferential direction in the land portion formed between the
wave-shaped main grooves, the plurality of lug grooves each
intersecting the tire circumferential direction and communicating
with the wave-shaped main grooves at both ends; and
a plurality of narrow grooves disposed between pairs of the
plurality of lug grooves adjacent in the tire circumferential
direction in a row in the tire circumferential direction, the
plurality of narrow grooves each intersecting the tire
circumferential direction, communicating with one of the main
grooves at a first end, terminating within the land portion at a
second end, and having a narrower groove width than the plurality
of lug grooves.
According to the pneumatic tire, two main grooves adjacent in the
tire lateral direction have a wave-like shape with periodic
oscillation. This increases the overall width of the main grooves
and provides good drainage properties, and allows braking
performance on wet road surfaces to be maintained. Furthermore,
according to the pneumatic tire, the lug grooves are disposed in a
row in the tire circumferential direction and communicate with the
wave-like main grooves at both ends. This allows good drainage
properties to be provided, and braking performance on wet road
surfaces to be maintained. Additionally, according to the pneumatic
tire, by the narrow grooves being disposed between pairs of the lug
grooves adjacent in the tire circumferential direction, good
drainage properties can be provided, the braking performance on wet
road surfaces can be maintained, and by the narrow grooves
communicating with the main groove at the first end and terminating
within the land portion at the second end and having a narrower
groove width than the lug grooves, a decrease in the rigidity of
the land portions between the wave-like main grooves can be
suppressed and wear resistance performance can be improved.
A pneumatic tire according to an embodiment of the present
technology may have a configuration wherein,
the plurality of main grooves in the tread surface comprises four
main grooves, each having periodic oscillation;
a center land portion, middle land portions adjacent to the center
land portion on either side in the tire lateral direction, and
shoulder land portions outwardly adjacent to the middle land
portions in the tire lateral direction are formed by the plurality
of main grooves; and
the center land portion and a first middle land portion of the
middle land portions comprise the plurality of lug grooves and the
plurality of narrow grooves.
According to the pneumatic tire, the center land portion and one of
the adjacent middle land portions on either side of the center land
portion in the tire lateral direction have good drainage
properties. This allows braking performance on wet road surfaces to
be maintained. Also, by suppressing a decrease in rigidity of the
center land portion and one of the adjacent middle land portions on
either side of the center land portion, the obtained effect of
improving wear resistance performance can be significant.
A pneumatic tire according to an embodiment of the present
technology may have a configuration wherein,
a second middle land portion of the middle land portions comprises
an auxiliary groove that extends in a linear manner in the tire
circumferential direction and has a narrower groove width than the
plurality of main grooves; and a plurality of middle land portion
narrow grooves disposed in a row in the tire circumferential
direction, the plurality of middle land portion narrow grooves each
intersecting the tire circumferential direction, communicating with
the main groove located outward in the tire lateral direction and
the auxiliary groove at both end portions, and having a narrower
groove width than the plurality of lug grooves.
According to the pneumatic tire, the second middle land portion
greatly contributes to drainage properties, and so by the second
middle land portion being provided with the auxiliary groove
extending in a linear manner in the tire circumferential direction
and the middle land portion narrow grooves, good drainage
properties can be provided, and thus the braking performance on wet
road surfaces can be improved. Furthermore, the auxiliary groove
has a narrower groove width than the main grooves, and the middle
land portion narrow grooves have a narrower groove width than the
lug grooves. Thus, a decrease in the rigidity of the middle land
portion can be suppressed, and wear resistance performance can be
improved.
A pneumatic tire according to an embodiment of the present
technology may have a configuration wherein,
the second middle land portion comprises a plurality of middle land
portion lug grooves disposed in a row in the tire circumferential
direction, the plurality of middle land portion lug grooves each
intersecting the tire circumferential direction, communicating with
the main groove located inward in the tire lateral direction at a
first end, and terminating within the second middle land portion at
a second end without reaching the auxiliary groove; and a plurality
of communication narrow grooves connecting terminating ends of the
plurality of middle land portion lug grooves to the auxiliary
groove and having a narrower groove width than the plurality of
middle land portion lug grooves.
According to the pneumatic tire, in the other middle land portion,
the other middle land portion is provided with the middle land
portion lug grooves that communicate with the main groove located
inward in the tire lateral direction at the first end and terminate
within the other middle land portion at the second end without
reaching the auxiliary groove and the communication narrow grooves
that connect the terminating ends of the middle land portion lug
groove and the auxiliary grooves. This provides good drainage
properties and allows braking performance on wet road surfaces to
be further maintained. Furthermore, the middle land portion lug
grooves that terminate within the middle land portion are provided
and the communication narrow grooves have a narrower groove width
than the middle land portion lug grooves. This allows a decrease in
the rigidity of the middle land portions to be suppressed and wear
resistance performance to be improved.
A pneumatic tire according to an embodiment of the present
technology may have a configuration further comprising, a plurality
of lug narrow grooves in which a lug groove and a narrow groove are
present disposed between the plurality of middle land portion lug
grooves and the plurality of communication narrow grooves.
According to the pneumatic tire, the lug narrow grooves are
disposed between the middle land portion lug grooves and the
communication narrow grooves. This allows excessive changes in
rigidity at the communicating portion between the middle land
portion lug grooves and the communication narrow grooves to be
suppressed, and wear resistance performance to be improved.
A pneumatic tire according to an embodiment of the present
technology may have a configuration wherein,
the shoulder land portions comprise a plurality of shoulder land
portion lug grooves disposed in a row in the tire circumferential
direction, the plurality of shoulder land portion lug grooves each
intersecting the tire circumferential direction and terminating
without reaching the main groove located inward of the shoulder
land portion in the tire lateral direction; and a shoulder land
portion narrow groove disposed between pairs of the plurality of
shoulder land portion lug grooves adjacent in the tire
circumferential direction, the shoulder land portion narrow groove
intersecting the tire circumferential direction, communicating with
the main groove located inward of the shoulder land portion in the
tire lateral direction at an end portion, and having a narrower
groove width than the plurality of shoulder land portion lug
grooves.
According to the pneumatic tire, the shoulder land portion lug
grooves provide good drainage properties in the shoulder land
portions, and the terminating ends within the shoulder land portion
allow a decrease in rigidity of the shoulder land portion to be
suppressed and wear resistance performance to be improved.
Furthermore, according to the pneumatic tire, the shoulder land
portion narrow grooves provide good drainage properties and allow
braking performance on wet road surfaces to be improved.
Additionally, the shoulder land portion narrow grooves have a
narrower groove width than the shoulder land portion lug grooves.
This allows a decrease in rigidity of the shoulder land portions to
be suppressed and wear resistance performance to be improved.
A pneumatic tire according to an embodiment of the present
technology may have a configuration wherein, in a first shoulder
land portion of the shoulder land portions, a plurality of the
shoulder land portion narrow grooves are disposed in a row in the
tire circumferential direction between pairs of the shoulder land
portion lug grooves adjacent in the tire circumferential
direction.
According to the pneumatic tire, the shoulder land portion narrow
grooves disposed in a row in the tire circumferential direction
provide good drainage properties and allow braking performance on
wet road surfaces to be improved.
A pneumatic tire according to an embodiment of the present
technology may have a configuration further comprising, a plurality
of communication narrow grooves connecting terminating ends of the
plurality of shoulder land portion lug grooves and the main groove
located inward of the shoulder land portion in the tire lateral
direction and having a narrower groove width than the plurality of
shoulder land portion lug grooves.
According to the pneumatic tire, the communication narrow grooves
that connect the terminating ends of the shoulder land portion lug
grooves and the main groove provide good drainage properties and
allow braking performance on wet road surfaces to be further
maintained. Furthermore, the shoulder land portion lug grooves that
terminate within the shoulder land portions are provided and the
communication narrow grooves have a narrower groove width than the
shoulder land portion lug grooves. This allows a decrease in the
rigidity of the shoulder land portions to be suppressed and wear
resistance performance to be improved.
A pneumatic tire according to an embodiment of the present
technology may have a configuration further comprising, a plurality
of lug narrow grooves in which a lug groove and a narrow groove are
present disposed between the plurality of shoulder land portion lug
grooves and the plurality of communication narrow grooves.
According to the pneumatic tire, the lug narrow grooves are
disposed between the shoulder land portion lug grooves and the
communication narrow grooves. This allows excessive changes in
rigidity at the communicating portion between the shoulder land
portion lug grooves and the communication narrow grooves to be
suppressed, and wear resistance performance to be improved.
A pneumatic tire according to an embodiment of the present
technology may have a configuration wherein, the main groove
located inward of a second shoulder land portion of the shoulder
land portions in the tire lateral direction comprises a plurality
of bulge grooves at positions corresponding to the plurality of
communication narrow grooves that bulge toward the adjacent second
middle land portion.
According to the pneumatic tire, the bulge grooves are provided
bulging toward the adjacent second middle land portion at positions
corresponding to the communication narrow grooves. This allows the
bulge grooves to function as a catchment for discharging water to
the communication narrow grooves, and allows braking performance on
wet road surfaces to be further maintained.
A pneumatic tire according to an embodiment of the present
technology may have a configuration wherein,
the shoulder land portions comprise a plurality of recessed
portions formed at an outer end in the tire lateral direction;
and
the plurality of shoulder land portion narrow grooves terminate at
the plurality of recessed portions at an outer end portion in the
tire lateral direction.
According to the pneumatic tire, the outer end portions of the
shoulder land portion narrow grooves in the tire lateral direction
terminate at the recessed portions. This prevents loads acting on
the outer end portions of the shoulder land portion narrow grooves
in the tire lateral direction, and allows a decrease in rigidity of
the shoulder land portions to be suppressed and wear resistance
performance to be improved.
A pneumatic tire according to an embodiment of the present
technology can provide enhanced wear resistance performance while
maintaining braking performance on wet road surfaces.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a meridian cross-sectional view of a pneumatic tire
according to an embodiment of the present technology.
FIG. 2 is a plan view of a tread portion of a pneumatic tire
according to an embodiment of the present technology.
FIG. 3 is an enlarged cross-sectional view of a main groove of a
pneumatic tire according to an embodiment of the present
technology.
FIG. 4 is an enlarged cross-sectional view of a lug groove of a
pneumatic tire according to an embodiment of the present
technology.
FIG. 5 is an enlarged cross-sectional view of a narrow groove of a
pneumatic tire according to an embodiment of the present
technology.
FIG. 6 is an enlarged cross-sectional view of a lug narrow groove
of a pneumatic tire according to an embodiment of the present
technology.
FIG. 7 is a plan view of a tread portion of a pneumatic tire of
another example according to an embodiment of the present
technology.
FIG. 8 is an enlarged cross-sectional view of a main groove of a
pneumatic tire according to another example of an embodiment of the
present technology.
FIG. 9 is a table showing the results of performance tests of
pneumatic tires according to Examples of the present
technology.
FIG. 10 is a table showing the results of performance tests on
pneumatic tires according to Examples of the present
technology.
DETAILED DESCRIPTION
Embodiments of the present technology are described in detail below
based on the drawings. However, the present technology is not
limited to these embodiments. Constituents of the embodiments
include elements that can be easily replaced by those skilled in
the art and elements substantially the same as the constituents of
the embodiments. Furthermore, the modified examples described in
the embodiments can be combined as desired within the scope
apparent to those skilled in the art.
FIG. 1 is a meridian cross-sectional view of a pneumatic tire
according to the present embodiment. FIG. 2 is a plan view of a
tread portion of the pneumatic tire according to the present
embodiment. FIG. 3 is an enlarged cross-sectional view of a main
groove of the pneumatic tire according to the present embodiment.
FIG. 4 is an enlarged cross-sectional view of a lug groove of the
pneumatic tire according to the present embodiment. FIG. 5 is an
enlarged cross-sectional view of a narrow groove of the pneumatic
tire according to the present embodiment. FIG. 6 is an enlarged
cross-sectional view of a lug narrow groove of the pneumatic tire
according to the present embodiment.
Herein, "tire radial direction" refers to the direction orthogonal
to the rotation axis (not illustrated) of a pneumatic tire 1.
"Inward in the tire radial direction" refers to the direction
toward the rotation axis in the tire radial direction. "Outward in
the tire radial direction" refers to the direction away from the
rotation axis in the tire radial direction. "Tire circumferential
direction" refers to the circumferential direction with the
rotation axis as the center axis. "Tire lateral direction" refers
to the direction parallel with the rotation axis. "Inward in the
tire lateral direction" refers to the direction toward a tire
equatorial plane (tire equator line) CL in the tire lateral
direction. "Outward in the tire lateral direction" refers to the
direction away from the tire equatorial plane CL in the tire
lateral direction. "Tire equatorial plane CL" refers to the plane
orthogonal to the rotation axis of the pneumatic tire 1 that passes
through the center of the tire width of the pneumatic tire 1. "Tire
width" is the width in the tire lateral direction between
components located outward in the tire lateral direction, or in
other words, the distance between the components that are the most
distant from the tire equatorial plane CL in the tire lateral
direction. "Tire equator line" refers to the line along the tire
circumferential direction of the pneumatic tire 1 that lies on the
tire equatorial plane CL. In the present embodiment, the tire
equator line and the tire equatorial plane are both denoted by
reference sign CL.
As illustrated in FIG. 1, the pneumatic tire 1 is mainly used on
passenger vehicles and includes a tread portion 2, shoulder
portions 3 on opposite sides of the tread portion 2, and sidewall
portions 4 and bead portions 5 continuing in that order from the
shoulder portions 3. The pneumatic tire 1 also includes a carcass
layer 6, a belt layer 7, and a belt reinforcing layer 8.
The tread portion 2 is made of rubber material (tread rubber), is
exposed on the outermost side of the pneumatic tire 1 in the tire
radial direction, and the surface thereof constitutes the contour
of the pneumatic tire 1. The outer circumferential surface of the
tread portion 2 is a tread surface 21 that mainly comes into
contact with a road surface when the tire runs.
The shoulder portions 3 are portions located outward in the tire
lateral direction on both sides of the tread portion 2.
Additionally, the sidewall portions 4 are exposed on the outermost
sides of the pneumatic tire 1 in the tire lateral direction. The
bead portions 5 each include a bead core 51 and a bead filler 52.
The bead core 51 is formed by a bead wire, which is a steel wire,
wound into an annular shape. The bead filler 52 is a rubber
material that is disposed in the space formed by an end of the
carcass layer 6 in the tire lateral direction folded back at the
position of the bead core 51.
The end portions of the carcass layer 6 in the tire lateral
direction are folded back around the pair of bead cores 51 from
inward to outward in the tire lateral direction, and the carcass
layer 6 is stretched in a toroidal shape in the tire
circumferential direction to form the framework of the tire. The
carcass layer 6 is constituted by a plurality of
coating-rubber-covered carcass cords (not illustrated) disposed in
alignment at an angle with respect to the tire circumferential
direction that conforms with the tire meridian direction. The
carcass cords are made of organic fibers (for example, polyester,
rayon, and nylon). At least one carcass layer 6 is provided.
The belt layer 7 has a multilayer structure in which at least two
belts 71, 72 are layered. In the tread portion 2, the belt layer 7
is disposed outward of the carcass layer 6 in the tire radial
direction, i.e. on the outer circumference thereof, and covers the
carcass layer 6 in the tire circumferential direction. The belts 71
and 72 each include a plurality of coating-rubber-covered cords
(not illustrated) disposed in alignment at a predetermined angle
with respect to the tire circumferential direction (for example,
from 20.degree. to 30.degree.. The cords are made of steel or
organic fibers (for example, polyester, rayon, and nylon).
Moreover, the belts 71 and 72 overlap each other and are disposed
so that the direction of the cords of the respective belts
intersect each other.
The belt reinforcing layer 8 is disposed outward of the belt layer
7 in the tire radial direction, i.e. on the outer circumference
thereof, and covers the belt layer 7 in the tire circumferential
direction. The belt reinforcing layer 8 includes a plurality of
coating-rubber-covered cords (not illustrated) disposed in
alignment in the tire lateral direction substantially
parallel)(.+-.5.degree.) with the tire circumferential direction.
The cords are made of steel or organic fibers (for example,
polyester, rayon, and nylon). The belt reinforcing layer 8
illustrated in FIG. 1 is disposed so as to cover end portions in
the tire lateral direction of the belt layer 7. The configuration
of the belt reinforcing layer 8 is not limited to that described
above. Although not illustrated in the drawings, a configuration
may be used in which the belt reinforcing layer 8 is disposed so as
to cover the entire belt layer 7. Alternatively, for example, a
configuration with two reinforcing layers may be used, in which the
inner reinforcing layer in the tire radial direction is formed
larger than the belt layer 7 in the tire lateral direction so as to
cover the entire belt layer 7, and the outer reinforcing layer in
the tire radial direction is disposed so as to only cover the end
portions of the belt layer 7 in the tire lateral direction. In
another example, a configuration with two reinforcing layers may be
used, in which both of the reinforcing layers are disposed so as to
only cover the end portions of the belt layer 7 in the tire lateral
direction. In other words, the belt reinforcing layer 8 overlaps
with at least the end portions of the belt layer 7 in the tire
lateral direction. Additionally, the belt reinforcing layer 8 is
constituted of a band-like strip material (having, for example, a
width of 10 mm) wound in the tire circumferential direction.
For the pneumatic tire 1 according to the present embodiment, the
vehicle inner/outer side orientation when the pneumatic tire 1 is
mounted to a vehicle is designated. In other words, when the
pneumatic tire 1 is mounted on a vehicle, the orientation with
respect to the inner side and the outer side of the vehicle in the
tire lateral direction is designated. While the designated
orientation is not illustrated in the drawings, the orientation is
indicated, for example, by an indicator provided on the sidewall
portion 4. For the pneumatic tire 1, the side facing the inner side
of the vehicle when mounted on the vehicle is referred to as a
"vehicle inner side" and a side facing the outer side of the
vehicle is referred to as a "vehicle outer side". Note that the
designations of the vehicle inner side and the vehicle outer side
are not limited to cases where the tire 1 is mounted on a vehicle.
For example, rims have an orientation with respect to the inner
side and outer side of the vehicle in the tire lateral direction.
Thus, when the pneumatic tire 1 is mounted on a rim, the
orientation with respect to the vehicle inner side and the vehicle
outer side in the tire lateral direction is designated.
As illustrated in FIGS. 1 and 2, in the pneumatic tire 1 as
described above, four main grooves 22 extending in the tire
circumferential direction are formed in the tread surface 21 of the
tread portion 2.
The main grooves 22 include two center main grooves 22A disposed
adjacent to the center in the tire lateral direction on either side
of the tire equatorial plane CL and shoulder main grooves 22B
disposed outward of the center main grooves 22A in the tire lateral
direction. Additionally, five land portions 23 are formed by the
main grooves 22 in the tread surface 21. The land portions 23
include a center land portion 23A disposed between the center main
grooves 22A and on the tire equatorial plane CL; middle land
portions 23B disposed between the center main grooves 22A and the
shoulder main grooves 22B and outwardly adjacent to the center land
portion 23A in the tire lateral direction; and shoulder land
portions 23C disposed outward of the shoulder main grooves 22B in
the tire lateral direction, outwardly adjacent to the middle land
portions 23B in the tire lateral direction, and outermost in the
tread portion 2 in the tire lateral direction.
The main grooves 22 (22A, 22B) have a wave-like shape with periodic
oscillation and a constant groove width W1 in the tire
circumferential direction. The wave-like shape of the main grooves
22 can be such that a groove bottom 22a illustrated in FIG. 3 has a
linear shape in the tire circumferential direction and groove walls
22b have periodic oscillation such that the groove width W1 is
constant in the tire circumferential direction. Alternatively, the
wave-like shape of the main grooves 22 can be such that the groove
bottom 22a and the groove walls 22b illustrated in FIG. 3 have
periodic oscillation such that the groove width W1 is constant in
the tire circumferential direction. In the present embodiment, as
illustrated in FIG. 3, the main grooves 22 are formed with a
chamfer 22c on the opening edges. The groove width W1 of the main
grooves 22 is the opening width to the tread surface 21. Thus, the
groove width W1 of the main grooves 22 with the chamfer 22c is the
groove width W1 between the outer edges of the chamfers 22c. As
illustrated in FIG. 3, the center main grooves 22A of the main
grooves 22 has a groove width W1 ranging from 5 mm to 12 mm and a
groove depth D1 ranging from 4 mm to 8 mm. The shoulder main
grooves 22B have a groove width W1 ranging from 3 mm to 6 mm and a
groove depth D1 ranging from 4 mm to 8 mm. The groove width W1 of
the center main grooves 22A is greater than that of the shoulder
main grooves 22B. For example, the groove width W1 of the shoulder
main grooves 22B ranges from 10% to 50% of the groove width W1 of
the center main grooves 22A. This is preferable to maintain the
drainage properties of the center main grooves 22A and to ensure
the rigidity of the land portions 23 around the shoulder main
grooves 22B. Additionally, as illustrated in FIG. 2, the center
main grooves 22A of the main grooves 22 have a central line 22d of
oscillation located a distance L1 outward from the tire equatorial
plane CL in the tire lateral direction, the distance L1 being a
distance ranging from 20% to 30% of a ground contact width TW. The
shoulder main grooves 22B have a central line 22d of oscillation
located a distance L2 outward from the tire equatorial plane CL in
the tire lateral direction, the distance L2 being a distance
ranging from 60% to 70% of the ground contact width TW. This is
preferable to maintain the drainage properties of the center main
grooves 22A and to ensure the rigidity of the land portions 23
around the shoulder main grooves 22B. The edge shape and dimensions
of the land portions 23 in the tire lateral direction can be
determined depending on the oscillation and position in the tire
lateral direction of the main grooves 22.
Herein, "ground contact width TW" refers to the width of the ground
contact region in the tire lateral direction. Additionally, the
outermost edges of the ground contact region in the tire lateral
direction are referred to as ground contact edges T. FIG. 2
illustrates the ground contact edges T as being continuous in the
tire circumferential direction. The ground contact region is the
region where the tread surface 21 of the tread portion 2 of the
pneumatic tire 1 comes into contact with a dry, flat road surface,
when the pneumatic tire 1 is mounted on a regular rim, inflated to
the regular internal pressure, and loaded with 70% of the regular
load. "Regular rim" refers to a "standard rim" defined by the Japan
Automobile Tyre Manufacturers Association Inc. (JATMA), a "design
rim" defined by the Tire and Rim Association, Inc. (TRA), or a
"measuring rim" defined by the European Tyre and Rim Technical
Organisation (ETRTO). "Regular internal pressure" refers to
"maximum air pressure" defined by JATMA, a maximum value given in
"TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" defined by
TRA, or "INFLATION PRESSURES" defined by ETRTO. "Regular load"
refers a "maximum load capacity" defined by JATMA, the maximum
value given in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION
PRESSURES" defined by TRA, and a "LOAD CAPACITY" defined by
ETRTO.
In the pneumatic tire 1 according to the present embodiment, the
middle land portion 23B on the vehicle inner side is provided with
an auxiliary groove 24 extending in a linear manner in the tire
circumferential direction. The auxiliary groove 24 has a smaller
groove width than the main groove 22 with the smallest groove width
W1. The auxiliary groove 24 is centrally disposed between the
center main groove 22A and the shoulder main groove 22B that form
the middle land portion 23B on the vehicle inner side. The
auxiliary groove 24 divides the middle land portion 23B on the
vehicle inner side into rib land portions adjacent in the tire
lateral direction. The auxiliary groove 24 has a groove width
ranging from 1 mm to less than 3 mm and a groove depth ranging from
4 mm to 8 mm.
In the pneumatic tire 1 according to the present embodiment, the
land portions 23 are provided with lug grooves 25 and narrow
grooves 26 that intersect the tire circumferential direction. The
lug grooves 25 provided in the center land portion 23A are referred
to as center land portion lug grooves 25A, the lug grooves 25
provided in the middle land portions 23B are referred to as middle
land portion lug grooves 25B, and the lug grooves 25 provided in
the shoulder land portions 23C are referred to as shoulder land
portion lug grooves 25C. The narrow grooves 26 provided in the
center land portion 23A are referred to as center land portion
narrow grooves 26A, the narrow grooves 26 provided in the middle
land portions 23B are referred to as middle land portion narrow
grooves 26B, and the narrow grooves 26 provided in the shoulder
land portions 23C are referred to as shoulder land portion narrow
grooves 26C. The narrow grooves 26 that communicate with a
terminating end of one of the lug grooves 25 and connect to one of
the main grooves 22 or the auxiliary grooves 24 are referred to as
communication narrow grooves 26E. Additionally, in the pneumatic
tire 1 according to the present embodiment, a lug narrow groove 27
is provided where both the lug groove 25 and the narrow groove 26
are present and connected.
As illustrated in FIG. 4, the lug groove 25 includes groove walls
25b formed with a chamfer 25c from the opening portion in the tread
surface 21 to a groove bottom 25a. The lug groove 25 has a groove
width W2 ranging from 2 mm to 4 mm and a groove depth D2 less than
that of the main grooves 22 and the auxiliary groove 24 ranging
from 2 mm to 6 mm. As illustrated in FIG. 5, the narrow groove 26
includes groove walls 26b formed from the opening portion in the
tread surface 21 to a groove bottom 26a in the tire radial
direction. The narrow groove 26 has a groove width W3 ranging from
0.4 mm to 1.0 mm and a groove depth D3 less than that of the main
grooves 22 and the auxiliary groove 24 ranging from 3 mm to 6 mm.
As illustrated in FIG. 6, the lug narrow groove 27 includes the lug
groove 25 and the narrow groove 26 formed in the groove bottom 25a
of the lug groove 25 in the extension direction of the lug groove
25. The sum of the groove depth D2 of the lug groove 25 and the
groove depth D3 of the narrow groove 26 makes an overall groove
depth of 6 mm or less, less than that of the main grooves 22 and
the auxiliary groove 24. Additionally, the groove depth D3 of the
narrow groove 26 of the lug narrow groove 27 is preferably 70% or
greater of the overall groove depth (D2+D3) of the lug narrow
groove 27 including the lug groove 25.
The center land portion lug grooves 25A provided in the center land
portion 23A are disposed in the tire circumferential direction. The
center land portion lug grooves 25A communicate at both ends with
the center main grooves 22A that form the center land portion 23A
and divide the center land portion 23A into a plurality of blocks
disposed in a row in the tire circumferential direction. Note that
in the present embodiment, the center land portion lug grooves 25A
are composed overall of the lug narrow grooves 27 where both the
lug grooves 25 and the narrow grooves 26 are present.
The middle land portion lug grooves 25B provided in the middle land
portion 23B on the vehicle outer side are disposed in the tire
circumferential direction. The middle land portion lug grooves 25B
communicate at both ends with the center main groove 22A and the
shoulder main groove 22B that form the middle land portion 23B on
the vehicle outer side and divide the middle land portion 23B on
the vehicle outer side into a plurality of blocks disposed in a row
in the tire circumferential direction. Additionally, the middle
land portion lug grooves 25B provided in the middle land portion
23B on the vehicle outer side communicate at one end with the
shoulder main groove 22B that forms the middle land portion 23B on
the vehicle outer side and terminates there. Note that in the
present embodiment, the middle land portion lug grooves 25B
provided in the middle land portion 23B on the vehicle outer side
are composed overall of the lug narrow grooves 27 where both the
lug grooves 25 and the narrow grooves 26 are present.
The middle land portion lug grooves 25B provided in the middle land
portion 23B on the vehicle inner side communicate at a first end
with the center main groove 22A that forms the middle land portions
23B on the vehicle inner side and terminates at a second end within
the middle land portion 23B on the vehicle inner side without
reaching the auxiliary groove 24. Accordingly, the middle land
portion 23B on the vehicle inner side is formed as a rib-like land
portion. Note that in the present embodiment, the middle land
portion lug grooves 25B provided in the middle land portion 23B on
the vehicle inner side are, at the terminating end portion, lug
narrow grooves 27 where both the lug grooves 25 and the narrow
grooves 26 are present. The communication narrow groove 26E extends
from the narrow groove 26 of the lug narrow groove 27 and
communicates with the auxiliary groove 24.
The middle land portion lug grooves 25B provided in the middle land
portion 23B on the vehicle outer side and the center land portion
lug grooves 25A provided in the center land portion 23A are
provided such that in a plan view they are one groove that passes
through the center main groove 22A on the vehicle outer side, with
both ends at the center main groove 22A between the middle land
portion 23B on the vehicle outer side and the center land portion
23A facing one another. The center land portion lug grooves 25A
provided in the center land portion 23A and the middle land portion
lug grooves 25B provided in the middle land portion 23B on the
vehicle inner side are provided such that in a plan view they are
one groove that passes through the center main groove 22A on the
vehicle inner side, with both ends at the center main groove 22A
between the center land portion 23A and the middle land portion 23B
on the vehicle inner side facing one another. Thus, the middle land
portion lug groove 25B provided in the middle land portion 23B on
the vehicle outer side, the center land portion lug groove 25A
provided in the center land portion 23A, and the middle land
portion lug groove 25B provided in the middle land portion 23B on
the vehicle inner side constitute one through lug grooves 25 that
passes through the center main grooves 22A. In other words, a
plurality of the through lug grooves 25E are provided in the tire
circumferential direction. The through lug grooves 25E intersect
the tire circumferential direction and pass through the center land
portion 23A and the middle land portion 23B on the vehicle outer
side. Also, the through lug grooves 25E open to the shoulder main
groove 22B on the vehicle outer side at a first end at the middle
land portion 23B on the vehicle outer side and pass through the
center main groove 22A on the vehicle inner side of the center land
portion 23A and terminate within the middle land portion 23B on the
vehicle inner side at a second end without reaching the auxiliary
groove 24.
The shoulder land portion lug grooves 25C provided in each of the
shoulder land portions 23C are disposed in a row in the tire
circumferential direction and intersect the tire circumferential
direction. The shoulder land portion lug grooves 25C open at a
first end to a design end E, which is the outer end of the tread
surface 21 of the tread portion 2 in the tire lateral direction,
and terminate at a second end within the shoulder land portion 23C
without reaching the shoulder main groove 22B located inward of the
shoulder land portion 23C in the tire lateral direction.
Accordingly, the shoulder land portions 23C are formed as rib-like
land portions. Note that in the present embodiment, the shoulder
land portion lug grooves 25C provided in the shoulder land portions
23C are, at the terminating end portion, lug narrow grooves 27
where both the lug grooves 25 and the narrow grooves 26 are
present. The communication narrow groove 26E extends from the
narrow groove 26 of the lug narrow groove 27 and communicates with
the shoulder main grooves 22B. Additionally, terminating end
portions of the shoulder land portion lug grooves 25C, which are
lug narrow grooves 27, are disposed on the ground contact edges
T.
Herein, design end E refers to the outermost end of the tread
portion 2 in the tire lateral direction disposed outward of the
ground contact edge T in the tire lateral direction, and is the
outermost end of the tread portion 2 in the tire lateral direction
where grooves are formed. In FIG. 2, the design end E is
illustrated as being continuous in the tire circumferential
direction. In other words, in the tread portion 2, when the tire is
placed on a dry, flat road surface, the region from the ground
contact edge T to the design end E is a region which does not
typically come into contact with the ground.
Note that the shoulder land portion lug grooves 25C provided in the
shoulder land portions 23C terminate within the shoulder land
portions 23C and are separated from the through lug grooves 25E
described above. However, the first end of the through lug groove
25E, i.e. the end of the middle land portion lug groove 25B
provided in the middle land portion 23B on the vehicle outer side
that communicates with the shoulder main groove 22B, is disposed on
an extension of the end portion where the shoulder land portion lug
groove 25C provided in the shoulder land portion 23C on the vehicle
outer side terminates within the shoulder land portion 23C.
Additionally, the second end of the through lug groove 25E, i.e.
the end of the middle land portion lug groove 25B provided in the
middle land portion 23B on the vehicle inner side, is disposed on
an extension of the end portion where the shoulder land portion lug
groove 25C provided in the shoulder land portion 23C on the vehicle
inner side terminates within the shoulder land portion 23C. In
other words, the lug grooves 25 that include the shoulder land
portion lug grooves 25C provided in the shoulder land portions 23C
and the through lug grooves 25E (the middle land portion lug
grooves 25B of the middle land portion 23B on the vehicle outer
side, the center land portion lug grooves 25A of the center land
portion 23A, and the middle land portion lug grooves 25B of the
middle land portion 23B on the vehicle inner side) are disposed on
a smooth, continuous curved line CU that crosses the land portions
23A, 23B, 23C between the outer ends (design ends E) of the tread
portion 2 in the tire lateral direction. Curved line CU refers to a
line having only tangent lines with an angle ranging from
40.degree. to 90.degree. with respect to the tire lateral
direction.
The center land portion narrow grooves 26A of the narrow grooves 26
provided in the center land portion 23A are disposed between
adjacent center land portion lug grooves 25A in the tire
circumferential direction and intersect the tire circumferential
direction. The center land portion narrow grooves 26A communicate
with the center main groove 22A on the vehicle inner side of the
center land portion 23A at a first end, and terminate within the
center land portion 23A at a second end without reaching the center
main groove 22A on the vehicle outer side of the center land
portion 23A. Additionally, a plurality of the center land portion
narrow grooves 26A are disposed in a row in the tire
circumferential direction between pairs of the center land portion
lug grooves 25A adjacent in the tire circumferential direction. In
the present embodiment, two center land portion narrow grooves 26A
are disposed in a row in the tire circumferential direction between
adjacent center land portion lug grooves 25A in the tire
circumferential direction. In an embodiment in which a plurality of
the center land portion narrow grooves 26A are disposed in a row in
the tire circumferential direction between adjacent center land
portion lug grooves 25A in the tire circumferential direction, the
first ends and the second ends of the center land portion narrow
grooves 26A alternate sides in order in the tire circumferential
direction. In other words, as illustrated in FIG. 2, uppermost
center land portion narrow groove 26A communicates with the center
main groove 22A on the vehicle outer side, the one under that
communicates with the center main groove 22A on the vehicle inner
side, and the one under that communicates with the center main
groove 22A on the vehicle outer side. Thus, the center land portion
narrow grooves 26 are disposed so to communicate with the main
grooves 22 on alternating sides in the tire lateral direction in
order in the tire circumferential direction.
The middle land portion narrow grooves 26B provided in the middle
land portion 23B on the vehicle outer side are disposed between
adjacent middle land portion lug grooves 25B in the tire
circumferential direction and intersect the tire circumferential
direction. The middle land portion narrow grooves 26B communicate
with the center main groove 22A at the middle land portion 23B at a
first end, and terminate within the middle land portions 23B at a
second end without reaching the shoulder main groove 22B at the
middle land portion 23B. A plurality of the middle land portion
narrow grooves 26B of the middle land portion 23B on the vehicle
outer side are disposed in a row in the tire circumferential
direction between pairs of the middle land portion lug grooves 25B
adjacent in the tire circumferential direction. In the present
embodiment, two middle land portion narrow grooves 26B of the
middle land portion 23B on the vehicle outer side are disposed in a
row in the tire circumferential direction between adjacent middle
land portion lug grooves 25B in the tire circumferential direction.
In an embodiment in which a plurality of the middle land portion
narrow grooves 26B of the middle land portion 23B on the vehicle
outer side are disposed in a row in the tire circumferential
direction between adjacent middle land portion lug grooves 25B in
the tire circumferential direction, the first ends and the second
ends of the middle land portion narrow grooves 26B alternate sides
in order in the tire circumferential direction. In other words, as
illustrated in FIG. 2, uppermost middle land portion narrow groove
26B of the middle land portion 23B communicates with the shoulder
main groove 22B, the one under that communicates with the center
main groove 22A, and the one under that communicates with the
shoulder main groove 22B on the vehicle outer side. Thus, the
middle land portion narrow groove 26B are disposed so to
communicate with the main grooves 22 on alternating sides in the
tire lateral direction in order in the tire circumferential
direction.
The middle land portion narrow grooves 26B provided in the middle
land portion 23B on the vehicle inner side are disposed between
extensions of adjacent middle land portion lug grooves 25B in the
tire circumferential direction and intersect the tire
circumferential direction. The middle land portion narrow grooves
26B communicate at both ends with the shoulder main groove 22B at
the middle land portion 23B and with the auxiliary groove 24. Thus,
the middle land portion narrow grooves 26B provided in the middle
land portion 23B on the vehicle inner side divide a portion of the
middle land portion 23B between the shoulder main groove 22B and
the auxiliary groove 24 into a plurality of blocks disposed in a
row in the tire circumferential direction.
The shoulder land portion narrow grooves 26C provided in the
shoulder land portions 23C are disposed between adjacent shoulder
land portion lug grooves 25C in the tire circumferential direction
and intersect the tire circumferential direction. The shoulder land
portion narrow grooves 26C communicate with the shoulder main
grooves 22B at a first end and terminate at a second end within the
shoulder land portions 23C near the outer ends of the tread portion
2 in the tire lateral direction (design ends E), extending beyond
the ground contact edges T.
A plurality of the shoulder land portion narrow grooves 26C
provided in the shoulder land portion 23C on the vehicle outer side
are disposed in a row in the tire circumferential direction between
adjacent shoulder land portion lug grooves 25C in the tire
circumferential direction. In the present embodiment, two shoulder
land portion narrow grooves 26C provided in the shoulder land
portion 23C on the vehicle outer side are disposed in a row in the
tire circumferential direction between adjacent shoulder land
portion lug grooves 25C in the tire circumferential direction.
Note that the shoulder land portions 23C are provided with recessed
portions 28 near the outer ends of the tread portion 2 in the tire
lateral direction (design ends E). The recessed portions 28 have a
circular dimple shape and are formed between adjacent shoulder land
portion lug grooves 25C in the tire circumferential direction in
two rows in the tire lateral direction, a laterally inner row 28a
with two recessed portions 28 in the tire circumferential direction
and a laterally outer row 28b with three recessed portions 28 in
the tire circumferential direction. Additionally, the recessed
portions 28 of the laterally outer row 28b have a larger diameter
than those of the laterally inner row 28a. The shoulder land
portion narrow grooves 26C provided in the shoulder land portions
23C terminate at the recessed portions 28 at the second ends. In
the present embodiment, the shoulder land portion narrow grooves
26C disposed in the shoulder land portion 23C on the vehicle inner
side terminate at the recessed portion 28 of the laterally outer
row 28b centrally located in the tire circumferential direction.
Additionally, the shoulder land portion narrow grooves 26C disposed
in the shoulder land portion 23C on the vehicle outer side
terminate at the recessed portion 28 of the laterally inner row
28a.
FIG. 7 is a plan view of a tread portion of a pneumatic tire
according to another example of the present embodiment.
A pneumatic tire 101 according to another example illustrated in
FIG. 7 is different from the pneumatic tire 1 described above in
that bulge grooves 22E are disposed in the shoulder main groove 22B
on the vehicle inner side; in that projections 31 are disposed in
the center main grooves 22A; in that the narrow grooves 26 of the
lug narrow grooves 27 of the center land portion 23A and the middle
land portion 23B on the vehicle outer side are zigzag narrow
grooves 26F; in that hole portions 32 are disposed in the center
land portion narrow grooves 26A of the center land portion 23A, the
middle land portion narrow grooves 26B of the middle land portion
23B on the vehicle outer side, and the shoulder land portion narrow
grooves 26C of the shoulder land portions 23C; and in that the
recessed portions 28 are disposed in the shoulder land portion 23C
on the vehicle outer side. How the pneumatic tire 101 is different
will be described below, and portions identical to those of the
pneumatic tire 1 described above are denoted with the same
reference signs and descriptions thereof are omitted.
A bulge groove 22E with a semi-circular bulge toward the middle
land portion 23B on the vehicle inner side is disposed in the
shoulder main groove 22B on the vehicle inner side. The bulge
groove 22E is disposed so as to bulge toward the middle land
portion 23B at a position corresponding to the communication narrow
groove 26E provided in the shoulder land portion 23C on the vehicle
inner side.
As illustrated in the enlarged cross-sectional view of a main
groove of FIG. 8, the projection 31 is provided projecting from the
groove bottom 22a of the center main groove 22A. The projection 31
has a hemispherical shape with a smooth curved surface that
projects from the groove bottom 22a of the center main groove 22A.
A plurality of the projections 31 are provided in the tire
circumferential direction in accord with the periodic oscillations
of the center main groove 22A. A plurality of rows (two in the
present embodiment) of projections 31 provided in the tire
circumferential direction in accord with the periodic oscillations
are provided in the tire lateral direction. The projections 31 are
formed with a lower projection height from the groove bottom 22a
than a wear indicator (not illustrated) disposed on the groove
bottom 22a of the center main groove 22A. The wear indicator is a
projection within the main groove 22 that allows the degree of wear
to be visually determined. The wear indicator of a tire for a
passenger vehicle has a specified height from the groove bottom 22a
of 1.6 mm. Thus, the projections 31 project from the groove bottom
22a with a height of less than 1.6 mm. Such a projection 31
preferably has a hemispherical shape with a diameter ranging from
0.4 mm to 1.5 mm and a projection height ranging from 0.2 mm to
less than 1.6 mm. Note that the projection 31 may also be provided
on the groove bottom 22a of the shoulder main grooves 22B.
Additionally, the projection 31 may also be provided on the groove
bottom 22a of only one of the shoulder main grooves 22B.
The zigzag narrow grooves 26F are narrow grooves 26 formed in a
zigzag shape provided in the groove bottom 25a of the lug grooves
25 of the lug narrow groove 27 of the center land portion 23A and
the middle land portion 23B on the vehicle outer side. The zigzag
narrow grooves 26F have a zigzag shape within the groove width W2
of the center land portion lug grooves 25A of the center land
portion 23A and the groove width W2 of the middle land portion lug
grooves 25B of the middle land portion 23B on the vehicle outer
side. The zigzag narrow grooves 26F have a groove width W3 and a
groove depth D3 similar to that of the narrow grooves 26 of the lug
narrow grooves 27 described above. The zigzag narrow grooves 26F
oscillate at least three or more times within one lug narrow groove
27. Additionally, one oscillation of the zigzag narrow grooves 26F
is formed by a short narrow groove and a long narrow groove. This
oscillation is repeated.
The hole portions 32 are disposed in the narrow grooves 26
including center land portion narrow grooves 26A of the center land
portion 23A, the middle land portion narrow grooves 26B of the
middle land portion 23B on the vehicle outer side, and the shoulder
land portion narrow grooves 26C of the shoulder land portions 23C.
The hole portions 32 expand the narrow grooves 26A, 26B, 26C in
parts, and preferably, for example, have a circular shape in a plan
view with a diameter ranging from 0.5 mm to 1.0 mm and a depth
ranging from 3 mm to 6 mm. The hole portions 32 are disposed in the
extension direction of the narrow grooves 26A, 26B, 26C. The center
land portion narrow grooves 26A of the center land portion 23A and
the middle land portion narrow grooves 26B of the middle land
portion 23B on the vehicle outer side terminate at one end within
the respective land portions 23A, 23B, and a total of three hole
portions 32 are disposed in each narrow groove 26A, 26B, with one
at the terminating end and a plurality (two in the present
embodiment) disposed partway along the narrow grooves 26A, 26B.
Note that as no recessed portions 28 are provided in the shoulder
land portion 23C on the vehicle outer side, the shoulder land
portion narrow grooves 26C of the shoulder land portion 23C on the
vehicle outer side terminate at the second end within the shoulder
land portion 23C on the vehicle outer side, and the hole portions
32 are provided at the terminating ends. Additionally, a total of
four hole portions 32 are disposed in each shoulder land portion
narrow groove 26C with a plurality (three in the present
embodiment) disposed partway along the shoulder land portion narrow
grooves 26C. In other words, the center land portion narrow grooves
26A of the center land portion 23A, the middle land portion narrow
grooves 26B of the middle land portion 23B on the vehicle outer
side, and the shoulder land portion narrow grooves 26C of the
shoulder land portion 23C on the vehicle outer side terminate at
the hole portions 32. Additionally, the shoulder land portion
narrow grooves 26C of the shoulder land portion 23C on the vehicle
inner side terminate at the second end at the recessed portions 28,
and a total of two hole portions 32 are disposed in each narrow
groove 26A with a plurality (two in the present embodiment)
disposed partway along the narrow groove 26C.
The hole portions 32 provided in the center land portion 23A and
the hole portions 32 provided in the middle land portion 23B on the
vehicle outer side are disposed in rows in the tire circumferential
direction and positioned offset in the tire lateral direction with
respect to straight lines SL (including the tire equator line CL)
in the tire circumferential direction. Specifically, the hole
portions 32 provided in the center land portion 23A and the hole
portions 32 provided in the middle land portion 23B on the vehicle
outer side are disposed in rows in the tire circumferential
direction and disposed partially on the straight lines SL
(including the tire equator line CL) in the tire circumferential
direction with positions offset in the tire lateral direction.
Additionally, the hole portions 32 provided in the shoulder land
portions 23C are disposed in rows in the tire circumferential
direction and positioned on the straight lines SL in the tire
circumferential direction without being offset in the tire lateral
direction. Note that the hole portions 32 are not disposed in the
middle land portion narrow grooves 26B of the middle land portion
23B on the vehicle inner side.
In such a manner, the pneumatic tire 1, 101 of the present
embodiment includes the tread surface 21 of the tread portion 2
including a plurality of main grooves 22 extending in the tire
circumferential direction and a plurality of land portions 23
adjacent to one another formed by the main grooves 22. At least two
main grooves 22 adjacent in the tire lateral direction have a
wave-like shape with periodic oscillation. The lug grooves 25 (the
center land portion lug grooves 25A and/or the middle land portion
lug grooves 25B on the vehicle outer side) are disposed in the land
portions(s) 23 formed between the wave-like main grooves 22 (the
center land portion 23A and/or the middle land portion 23B on the
vehicle outer side) in a row in the tire circumferential direction,
intersect the tire circumferential direction, and communicate with
the main grooves 22 at both ends. The narrow grooves 26 (the center
land portion narrow grooves 26A and/or the middle land portion
narrow grooves 26B on the vehicle outer side) are disposed between
pairs of the lug grooves 25 adjacent in the tire circumferential
direction in a row in the tire circumferential direction, intersect
the tire circumferential direction, and have a narrower groove
width than the lug grooves 25.
According to the pneumatic tire 1, 101, two main grooves 22
adjacent in the tire lateral direction have a wave-like shape with
periodic oscillation. This increases the overall width of the main
grooves 22 and provides good drainage properties, and allows
braking performance on wet road surfaces to be maintained.
Furthermore, according to the pneumatic tire 1, 101, the lug groove
25 are disposed in a row in the tire circumferential direction and
communicate with the wave-like main grooves 22 at both ends. This
allows good drainage properties to be provided, and braking
performance on wet road surfaces to be maintained. Additionally,
according to the pneumatic tire 1, 101, by the narrow grooves 26
being disposed between pairs of the lug grooves 25 adjacent in the
tire circumferential direction, good drainage properties can be
provided, the braking performance on wet road surfaces can be
maintained, and by the narrow grooves 26 communicating with the
main groove 22 at the first end and terminating within the land
portion 23 at the second end and having a narrower groove width
than the lug grooves 25, a decrease in the rigidity of the land
portions 23 between the wave-like main grooves 22 can be suppressed
and wear resistance performance can be improved.
Preferably, in the pneumatic tire 1, 101 of the present embodiment,
four main grooves 22 are provided in the tread surface 21, each
having periodic oscillation. The main grooves 22 form the center
land portion 23A, the middle land portions 23B adjacent to the
center land portion 23A on either side in the tire lateral
direction, and the shoulder land portions 23C outwardly adjacent to
the middle land portions 23B in the tire lateral direction. The
center land portion 23A and one of the middle land portions 23B (on
the vehicle outer side) are provided with the lug grooves 25 and
the narrow grooves 26.
According to the pneumatic tire 1, 101, the center land portion 23A
and one of the adjacent middle land portions 23B on either side of
the center land portion 23A in the tire lateral direction have good
drainage properties. This allows braking performance on wet road
surfaces to be maintained. Also, by suppressing a decrease in
rigidity of the center land portion 23A and one of the adjacent
middle land portions 23B on either side of the center land portion
23A, the obtained effect of improving wear resistance performance
can be significant.
Preferably, in the pneumatic tire 1, 101 of the present embodiment,
the other middle land portion 23B (on the vehicle inner side) is
provided with the auxiliary groove 24 having a narrower groove
width than the main grooves 22 and extending in a linear manner in
the tire circumferential direction; and the middle land portion
narrow grooves 26B disposed in a row in the tire circumferential
direction that intersect the tire circumferential direction, the
middle land portion narrow grooves 26B each communicating with the
main groove 22 located outwardly adjacent in the tire lateral
direction and the auxiliary groove 24 at both ends and having a
narrower groove width than the lug grooves 25.
According to the pneumatic tire 1, 101, the middle land portion 23B
greatly contribute to drainage properties, and so by the middle
land portion 23B being provided with the auxiliary groove 24
extending in a linear manner in the tire circumferential direction
and the middle land portion narrow grooves 26B, good drainage
properties are provided, and thus the braking performance on wet
road surfaces can be improved. Furthermore, the auxiliary groove 24
has a narrower groove width than the main grooves 22, and the
middle land portion narrow grooves 26B have a narrower groove width
than the lug grooves 25. Thus, a decrease in the rigidity of the
middle land portion 23B can be suppressed, and wear resistance
performance can be improved.
Preferably, in the pneumatic tire 1, 101 of the present embodiment,
the other middle land portion 23B (on the vehicle inner side) is
provided with the middle land portion lug grooves 25B disposed in a
row in the tire circumferential direction, the middle land portion
lug grooves 25B intersecting the tire circumferential direction,
communicating with the main groove 22 located inward in the tire
lateral direction at the first end, and terminating within the
other middle land portion 23B at the second end without reaching
the auxiliary groove 24; and the communication narrow grooves 26E
connecting the terminating ends of the middle land portion lug
grooves 25B and the auxiliary groove 24 and having a narrower
groove width than the middle land portion lug grooves 25B.
According to the pneumatic tire 1, 101, in the other middle land
portion 23B, the other middle land portion 23B is provided with the
middle land portion lug grooves 25B that communicate with the main
groove 22 located inward in the tire lateral direction at the first
end and terminate within the other middle land portion 23B at the
second end without reaching the auxiliary groove 24 and the
communication narrow grooves 26E that connect the terminating ends
of the middle land portion lug groove 25B and the auxiliary grooves
24. This provides good drainage properties and allows braking
performance on wet road surfaces to be further maintained.
Furthermore, the middle land portion lug grooves 25B that terminate
within the middle land portion 23B are provided and the
communication narrow grooves 26E have a narrower groove width than
the middle land portion lug grooves 25B. This allows a decrease in
the rigidity of the middle land portions 23B to be suppressed and
wear resistance performance to be improved.
Preferably, in the pneumatic tire 1, 101 according to the present
embodiment, the lug narrow grooves 27 in which the lug groove 25
and the narrow groove 26 are present are disposed between the
middle land portion lug grooves 25B and the communication narrow
grooves 26E.
According to the pneumatic tire 1, 101, the lug narrow grooves 27
are disposed between the middle land portion lug grooves 25B and
the communication narrow grooves 26E. This allows excessive changes
in rigidity at the communicating portion between the middle land
portion lug grooves 25B and the communication narrow grooves 26E to
be suppressed, and wear resistance performance to be improved.
Preferably, in the pneumatic tire 1, 101 of the present embodiment,
the shoulder land portions 23C are provided with the shoulder land
portion lug grooves 25C disposed in a row in the tire
circumferential direction that intersect the tire circumferential
direction, the shoulder land portion lug grooves 25C terminating
without reaching the main groove 22 located inward in the tire
lateral direction of the shoulder land portion 23C (the shoulder
main groove 22B); and the shoulder land portion narrow grooves 26C
disposed between pairs of the shoulder land portion lug grooves 25C
adjacent in the tire circumferential direction that intersect the
tire circumferential direction, the shoulder land portion narrow
grooves 26C communicating with the main groove 22 located inward of
the shoulder land portion 23C in the tire lateral direction at an
end portion and having a narrower groove width than the shoulder
land portion lug grooves 25C.
According to the pneumatic tire 1, 101, the shoulder land portion
narrow grooves 26C provide good drainage properties in the shoulder
land portions 23C, and the terminating ends within the shoulder
land portion 23C allow a decrease in rigidity of the shoulder land
portion 23C to be suppressed and wear resistance performance to be
improved. Furthermore, according to the pneumatic tire 1, 101, the
shoulder land portion narrow grooves 26C provide good drainage
properties and allow braking performance on wet road surfaces to be
improved. Additionally, the shoulder land portion narrow grooves
26C have a narrower groove width than the shoulder land portion lug
grooves 25C. This allows a decrease in rigidity of the shoulder
land portions 23C to be suppressed and wear resistance performance
to be improved.
Preferably, in the pneumatic tire 1, 101 of the present embodiment,
the shoulder land portion narrow grooves 26C are provided in one of
the shoulder land portions 23C (on the vehicle outer side) disposed
between pairs of the shoulder land portion lug grooves 25C adjacent
in the tire circumferential direction in a row in the tire
circumferential direction.
According to the pneumatic tire 1, 101, the shoulder land portion
narrow grooves 26C disposed in a row in the tire circumferential
direction provide good drainage properties and allow braking
performance on wet road surfaces to be improved.
Preferably, in the pneumatic tire 1, 101 of the present embodiment,
the communication narrow grooves 26E are provided connecting the
terminating ends of the shoulder land portion lug grooves 25C and
the main groove 22 located inward of the shoulder land portion 23C
in the tire lateral (the shoulder main groove 22B), and have a
narrower groove width than the shoulder land portion lug grooves
25C.
According to the pneumatic tire 1, 101, the communication narrow
grooves 26E that connect the terminating ends of the shoulder land
portion lug grooves 25C and the main groove 22 provide good
drainage properties and allow braking performance on wet road
surfaces to be further maintained. Furthermore, the shoulder land
portion lug grooves 25C that terminate within the shoulder land
portions 23C are provided and the communication narrow grooves 26E
have a narrower groove width than the shoulder land portion lug
grooves 25C. This allows a decrease in the rigidity of the shoulder
land portions 23C to be suppressed and wear resistance performance
to be improved.
Preferably, in the pneumatic tire 1, 101 according to the present
embodiment, the lug narrow grooves 27 in which the lug groove 25
and the narrow groove 26 are present are disposed between the
shoulder land portion lug grooves 25C and the communication narrow
grooves 26E.
According to the pneumatic tire 1, 101, the lug narrow grooves 27
are disposed between the shoulder land portion lug grooves 25C and
the communication narrow grooves 26E. This allows excessive changes
in rigidity at the communicating portion between the shoulder land
portion lug grooves 25C and the communication narrow grooves 26E to
be suppressed, and wear resistance performance to be improved.
Preferably, in the pneumatic tire 101 of the present embodiment,
the main groove 22 (the shoulder main groove 22B) located inward of
one of the shoulder land portions 23C (on the vehicle inner side)
in the tire lateral direction is provided with the bulge grooves
22E that bulge toward the other adjacent middle land portion 23B
(on the vehicle inner side) at positions corresponding to the
communication narrow grooves 26E.
According to the pneumatic tire 101, the bulge grooves 22E are
provided bulging toward the other adjacent middle land portion 23B
(on the vehicle inner side) at positions corresponding to the
communication narrow grooves 26E. This allows the bulge grooves 22E
to function as a catchment for discharging water to the
communication narrow grooves 26E, and allows braking performance on
wet road surfaces to be further maintained.
Preferably, in the pneumatic tire 1, 101 of the present embodiment,
the shoulder land portions 23C are provided with recessed portions
28 at the outer ends in the tire lateral direction, and the
shoulder land portion narrow grooves 26C terminate at the recessed
portions 28 at the outer end portion in the tire lateral
direction.
According to the pneumatic tire 1, 101, the outer end portions of
the shoulder land portion narrow grooves 26C in the tire lateral
direction terminate at the recessed portions 28. This prevents
loads acting on the outer end portions of the shoulder land portion
narrow grooves 26C in the tire lateral direction, and allows a
decrease in rigidity of the shoulder land portions 23C to be
suppressed and wear resistance performance to be improved.
The pneumatic tire 101 of the present embodiment includes the tread
surface 21 of the tread portion 2 including the main grooves 22
extending in the tire circumferential direction and the land
portions 23 adjacent to one another in the tire lateral direction
formed by the main grooves 22. At least one of the main grooves 22
has a wave-like shape with periodic oscillation. The groove bottom
22a of the wave-like main groove 22 is provided with the
projections 31 disposed in a row in the tire circumferential
direction in accord with the periodic oscillations of the main
groove 22.
According to the pneumatic tire 101, the main grooves 22 have a
wave-like shape with periodic oscillation. This increases the
overall width of the main grooves 22 and provides good drainage
properties, and allows braking performance on wet road surfaces to
be improved. Furthermore, according to the pneumatic tire 101, the
projections 31 provided on the groove bottom 22a of the wave-like
main grooves 22 makes the water at the groove bottom 22a of the
main groove 22 turbulent to spread out and discharge the water out
of the main groove 22. This allows good drainage properties to be
provided and braking performance on wet road surfaces to be
improved.
Preferably, in the pneumatic tire 101 of the present embodiment,
the projections 31 are disposed in a plurality of rows in the tire
lateral direction.
According to the pneumatic tire 101, the projections 31 are
disposed in rows in the tire lateral direction. This allows the
water located outward of the main groove 22 in the tire lateral
direction to be spread out and discharged.
Thus, drainage properties can be further improved and braking
performance on wet road surfaces can be improved.
Preferably, in the pneumatic tire 101 of the present embodiment,
the projections 31 are formed with a lower projection height from
the groove bottom 22a than a wear indicator disposed on the groove
bottom 22a of the main groove 22.
According to the pneumatic tire 101, the projections 31 are formed
with a lower projection height from the groove bottom 22a than a
wear indicator, which is a projection within the main groove 22
that allows the degree of wear to be visually determined. This
prevents the function of the wear indicator being inhibited by the
projections 31.
Preferably, in the pneumatic tire 101 of the present embodiment,
four main grooves 22 are provided in the tread surface 21, each
having periodic oscillation. The main grooves 22 form the center
land portion 23A, the middle land portions 23B adjacent to the
center land portion 23A on either side in the tire lateral
direction, and the shoulder land portions 23C outwardly adjacent to
the middle land portions 23B in the tire lateral direction. The
projections 31 are disposed in the main grooves 22 (center main
groove 22A) between the center land portion 23A and the middle land
portions 23B.
According to the pneumatic tire 101, the projections 31 are
disposed to provide good drainage properties in the main grooves 22
between the middle land portions 23B on either side of the center
land portion 23A, which is the center land portion 23A in the
center of the tread surface 21 that contributes to the braking
performance on wet road surfaces. This allows a significant effect
of improving braking performance on wet road surfaces to be
obtained.
The pneumatic tire 101 of the present embodiment includes the tread
surface 21 of the tread portion 2 including the main grooves 22
extending in the tire circumferential direction and the land
portions 23 adjacent to one another formed by the main grooves 22.
Adjacent main grooves 22 in the tire lateral direction have a
wave-like shape with periodic oscillation. The lug grooves 25 are
disposed in the land portions 23 formed between the wave-like main
grooves 22 adjacent in the tire lateral direction in a row in the
tire circumferential direction, intersect the tire circumferential
direction, and communicate with the main grooves 22 at both ends.
The zigzag narrow grooves 26F are disposed in the groove bottoms
25a of the lug grooves 25 with a zigzag shape in the extension
direction of the lug grooves 25 and have a narrower groove width
than the lug grooves 25.
According to the pneumatic tire 101, the main grooves 22 have a
wave-shape with periodic oscillation. This increases the overall
width of the main grooves 22 and provides good drainage properties,
and allows braking performance on wet road surfaces to be
maintained. Furthermore, according to the pneumatic tire 101, the
lug grooves 25 and the zigzag narrow grooves 26F provide good
drainage properties, and how the zigzag narrow grooves 26F mate
suppresses a decrease in rigidity of the land portions 23 divided
by the lug grooves 25. This allows wear resistance performance to
be improved.
Preferably, in the pneumatic tire 101 of the present embodiment,
the zigzag narrow grooves 26F have the groove depth D3 which is 70%
or greater of the overall groove depth of the lug groove 25
including the groove depth D2.
According to the pneumatic tire 101, the zigzag narrow grooves 26F
have a groove depth that is 70% or greater of the overall groove
depth. This allows a significant effect of providing good drainage
properties and a significant effect of improving wear resistance
performance to be obtained.
Preferably, in the pneumatic tire 101 of the present embodiment,
the zigzag narrow grooves 26F oscillate at least three or more
times.
According to the pneumatic tire 101, the zigzag narrow grooves 26F
oscillate three or more times. This allows the obtained effect of
improving wear resistance performance to be significant.
Preferably, one oscillation of the zigzag narrow grooves 26F is
formed by a short narrow groove and a long narrow groove, and this
oscillation is repeated. This allows a decrease in rigidity of the
land portions 23 divided by the lug grooves 25 to be further
suppressed, and the obtained effect of improving wear resistance
performance to be more significant.
Preferably, in the pneumatic tire 101 of the present embodiment,
four main grooves 22 are provided in the tread surface 21, each
having periodic oscillation. The main grooves 22 form the center
land portion 23A, the middle land portions 23B adjacent to the
center land portion 23A on either side in the tire lateral
direction, and the shoulder land portions 23C outwardly adjacent to
the middle land portions 23B in the tire lateral direction. The
center land portion 23A and one of the middle land portions 23B (on
the vehicle outer side) are provided with the lug grooves 25 and
the zigzag narrow grooves 26F. The other middle land portion 23B
(on the vehicle inner side) and the shoulder land portion 23C are
provided with the lug grooves 25 without a zigzag narrow groove 26F
disposed in a row in the tire circumferential direction that
intersect the tire circumferential direction. The lug grooves 25
are disposed on the smooth, continuous curved line CU that crosses
the land portions 23A, 23B, 23C between the outer ends of the tread
portion 2 in the tire lateral direction.
According to the pneumatic tire 101, the lug grooves 25 are
disposed on the smooth, continuous curved line CU that crosses the
land portions 23A, 23B, 23C between the outer ends of the tread
portion 2 in the tire lateral direction. This allows good drainage
properties to be provided between the land portions 23A, 23B, 23C,
and braking performance on wet road surfaces to be maintained.
Furthermore, the lug grooves 25 are disposed on the smooth,
continuous curved line CU that crosses the land portions 23A, 23B,
23C between the outer ends of the tread portion 2 in the tire
lateral direction. This allows an excessive difference in rigidity
between the land portions 23A, 23B, 23C in the tire lateral
direction to be suppressed. Thus, wear resistance performance can
be improved.
Additionally, the pneumatic tire 101 of the present embodiment
includes the tread surface 21 of the tread portion 2 provided with
a plurality of main grooves 22 extending in the tire
circumferential direction and a plurality of land portions 23
adjacent to one another formed by the main grooves 22. The main
grooves 22 have a wave-like shape with periodic oscillation. The
lug grooves 25 are disposed in the land portions 23 in a row in the
tire circumferential direction and intersect the tire
circumferential direction. The narrow grooves 26 are disposed
between pairs of the lug grooves 25 adjacent in the tire
circumferential direction in a row in tire circumferential
direction, intersect the tire circumferential direction, and have a
narrower groove width than the lug grooves 25. The hole portions 32
are formed in the narrow grooves 26.
According to the pneumatic tire 101, the main grooves 22 have a
wave-like shape with periodic oscillation. This increases the
overall width of the main grooves 22 and provides good drainage
properties, and allows braking performance on wet road surfaces to
be maintained. Additionally, according to the pneumatic tire 101,
in addition to providing good drainage properties with the lug
grooves 25 and the narrow grooves 26, a decrease in the rigidity of
the land portions 23 is suppressed by the narrow grooves 26 having
a groove width less than that of the lug grooves 25. As a result,
wear resistance performance can be improved. Also, the effect of
suppressing a decrease in the rigidity of the land portions 23 is
maintained by the narrow grooves 26, and the hole portions 32
further improve drainage properties. As a result, braking
performance on wet road surfaces can be maintained.
Preferably, in the pneumatic tire 101 of the present embodiment,
four main grooves 22 are provided in the tread surface 21, each
having periodic oscillation. The main grooves 22 form the center
land portion 23A, the middle land portions 23B adjacent to the
center land portion 23A on either side in the tire lateral
direction, and the shoulder land portions 23C outwardly adjacent to
the middle land portions 23B in the tire lateral direction. A
plurality of narrow grooves 26 including the hole portions 32 are
disposed in the center land portion 23A and one of the middle land
portions 23B (on the vehicle outer side) in a row in the tire
circumferential direction. The narrow grooves 26 having the hole
portions 32 communicate with one of the main grooves 22 at the
first end and terminate within the land portion 23 at the second
end without reaching the other main groove 22, with the first ends
and the second ends alternating sides in the tire lateral direction
in the tire circumferential direction.
According to the pneumatic tire 101, the center land portion 23A
and one of the middle land portions 23B (on the vehicle outer side)
are land portions 23 that contribute to braking performance on wet
road surfaces. The narrow grooves 26 having the hole portions 32
disposed in the land portions 23A, 23B in a row in the tire
circumferential direction provide good drainage properties and
improve braking performance on wet road surfaces. By the narrow
grooves 26 having the hole portions 32 terminating within the land
portion 23 at the second end and having the first end and second
end alternating sides in the tire lateral direction in the tire
circumferential direction, the rigidity of the land portions 23 can
be made uniform. As a result, wear resistance performance can be
improved.
Preferably, in the pneumatic tire 101 according to the present
embodiment, the hole portions 32 provided in the center land
portion 23A and the hole portions 32 provided in one of the middle
land portions 23B (on the vehicle outer side) are disposed in rows
in the tire circumferential direction and positioned offset in the
tire lateral direction with respect to straight lines SL in the
tire circumferential direction.
According to the pneumatic tire 101, by the hole portions 32 having
positions offset in the tire lateral direction with respect to the
straight lines SL in the tire circumferential direction, cracking
between the hole portions 32 in the tire circumferential direction
between the narrow grooves 26 disposed in a row in the tire
circumferential direction can be suppressed.
Preferably, in the pneumatic tire 101 according to the present
embodiment, the hole portions 32 provided in the center land
portion 23A and the hole portions 32 provided in one of the middle
land portions 23B (on the vehicle outer side) are disposed in rows
in the tire circumferential direction and disposed partially on the
straight lines SL in the tire circumferential direction with
positions offset in the tire lateral direction.
According to the pneumatic tire 101, by the hole portions 32 having
positions offset in the tire lateral direction with respect to the
straight lines SL in the tire circumferential direction, cracking
between the hole portions 32 in the tire circumferential direction
between the narrow grooves 26 disposed in a row in the tire
circumferential direction can be suppressed. By the hole portions
32 being disposed partially on the straight lines SL in the tire
circumferential direction, this offset positioning in the tire
circumferential direction of the hole portions 32 suppresses
non-uniformity of the rigidity of the center land portion 23A and
one of the middle land portions 23B (on the vehicle outer side). As
a result, wear resistance performance can be improved.
Preferably in the pneumatic tire 101 of the present embodiment, the
shoulder land portions 23C are provided with the narrow grooves 26
including the hole portions 32.
According to the pneumatic tire 101, in addition to providing good
drainage properties in the shoulder land portions 23C with the
narrow grooves 26, a decrease in the rigidity of the shoulder land
portions 23C is suppressed by the narrow grooves 26 having a groove
width less than that of the lug grooves 25. As a result, wear
resistance performance can be improved. Also, an effect of
suppressing a decrease in the rigidity of the land portions 23 is
maintained by the narrow grooves 26, and the hole portions 32
further improve drainage properties. As a result, braking
performance on wet road surfaces can be maintained.
Preferably in the pneumatic tire 101 of the present embodiment, the
hole portions 32 provided in the shoulder land portions 23C are
disposed in rows in the tire circumferential direction and
positioned on the straight lines SL in the tire circumferential
direction.
According to the pneumatic tire 101, non-uniformity of the rigidity
of the shoulder land portions 23C in the tire circumferential
direction caused by the positions of the hole portions 32 can be
suppressed, and thus wear resistance performance can be
improved.
Preferably, in the pneumatic tire 101 of the present embodiment,
the other middle land portion 23B (on the vehicle inner side) is
provided with the auxiliary groove 24 having a narrower groove
width than the main grooves 22 and extending in a linear manner in
the tire circumferential direction, and the middle land portion
narrow grooves 26B without the hole portions 32 that communicate
with the main groove 22 located outwardly adjacent in the tire
lateral direction and the auxiliary groove 24 at both ends and have
a narrower groove width than the lug grooves 25.
According to the pneumatic tire 101, the middle land portion 23B
greatly contribute to drainage properties, and so by the middle
land portion 23B being provided with the auxiliary groove 24
extending in a linear manner in the tire circumferential direction
and the middle land portion narrow grooves 26B, good drainage
properties can be provided, and thus the braking performance on wet
road surfaces can be improved. Furthermore, the middle land portion
23B, though including the auxiliary groove 24, is not provided with
the hole portions 32. Thus, a decrease in the rigidity of the
middle land portion 23B can be suppressed, and wear resistance
performance can be improved.
EXAMPLES
In the examples, performance tests for wear resistance performance
and braking performance on wet road surfaces were performed on a
plurality of types of pneumatic tires of different conditions (see
FIGS. 9 and 10).
In these performance tests, pneumatic tires having a tire size of
205/55R16 were assembled on 16.times.65J rims, inflated to the
regular internal pressure (200 kPa), and mounted on a test vehicle
(1600 cc, front engine front wheel drive sedan passenger
vehicle).
Wear resistance performance was evaluated by driving the test
vehicle described above on a test course with a dry road surface
for 5000 km and then measuring the wear of the land portions via
the amount of main groove remaining. Then, the measurement results
were expressed as index values with the value of Conventional
Example being defined as the reference (100). In this evaluation,
larger values indicate less wear, which is preferable.
Braking performance on wet road surfaces was evaluated by measuring
the braking distance of the test vehicle from a speed of 100 km/h
on a wet road surface test course with a water depth of 1 mm. Then,
the measurement results were expressed as index values with the
value of the Conventional Example being defined as the reference
(100). In this evaluation, larger values indicate less braking
distance, which is preferable.
In FIGS. 9 and 10, the pneumatic tires that were used as the test
tires had a configuration including five land portions formed by
four main grooves on the tread surface, the land portions including
the center land portion disposed on the tire equatorial plane CL,
the middle land portions disposed adjacent to the center land
portion on the two sides in the tire lateral direction, and the
shoulder land portions disposed adjacent to the middle land
portions on the outer sides in the tire lateral direction.
The pneumatic tire of Conventional Example indicated in FIG. 9
include main grooves that oscillate in a wave-like manner. In the
conventional pneumatic tire, the lug grooves communicate with the
land portions at both ends. Additionally, in the conventional
pneumatic tire, the narrow grooves disposed in the center land
portion and the middle land portions are sets of two, each
communicating with the main grooves at both ends.
In the pneumatic tires of Examples 1 to 12 indicated in FIGS. 9 and
10, the main grooves oscillate in a wave-like manner, the lug
grooves communicate with the land portions at both ends, and the
narrow grooves of the center land portion and the middle land
portions are sets of two with the second end portion terminating
within the land portion. The pneumatic tires of Examples 3 to 12
include the lug grooves and the narrow grooves described above in
the center land portion and one of the middle land portions (on the
vehicle outer side). The pneumatic tires of Examples 4 to 12
include an auxiliary groove and narrow grooves that communicate
with the main groove and the auxiliary groove at both end portions
disposed in the other middle land portion (on the vehicle inner
side). The pneumatic tires of Examples 5 to 12 include lug grooves
that communicate with the main groove at the first end and
terminate within the middle land portion at the second end (one of
the end portions) without reaching the auxiliary groove, and
communication narrow grooves that communicate with the terminating
ends of the lug grooves. In the pneumatic tires of Examples 6 to
12, lug narrow grooves in which a lug groove and a narrow groove
are present are disposed between the lug grooves of the other
middle land portion (on the vehicle inner side) and the
communication narrow groove. The pneumatic tire of Examples 7 to 12
include, in the shoulder land portions, lug grooves that terminate
without communicating with the main grooves and one narrow groove
disposed between each lug groove that communicates with the main
groove at one end portion. The pneumatic tires of Examples 8 to 12
include, in one of the shoulder land portions (on the vehicle outer
side), two narrow grooves disposed in the tire circumferential
direction in a row in between pairs of lug grooves. The pneumatic
tires of Examples 9 to 12 include, in the shoulder land portions,
communication narrow grooves that communicate with terminating ends
of the lug grooves and the main grooves. In the pneumatic tires of
Examples 10 to 12, in the shoulder land portions, lug narrow groove
in which a lug groove and a narrow groove is present are disposed
between the lug grooves and the communication narrow grooves. In
the pneumatic tires of Example 11 and 12, the main groove located
inward of the other shoulder land portion (on the vehicle inner
side) in the tire lateral direction is provided with bulge grooves
that bulge toward the other adjacent middle land portion (on the
vehicle inner side) at positions corresponding to the communication
narrow grooves. In the pneumatic tire of Example 12, in the
shoulder land portions, recessed portions are formed at the outer
ends in the tire lateral direction, and the narrow grooves
terminate at the recessed portions.
As can be seen from the test results of FIGS. 9 and 10, the
pneumatic tires of Examples 1 to 12 provided enhanced wear
resistance performance while maintaining braking performance on wet
road surfaces.
* * * * *